Many legitimate companies take advantage of poorly written contracts for monetary gain. The terms state the DAO's code is the contract. It's just as if he was a lawyer or analyst, who did his due diligence, carefully reading the contract and finding a (legal) loophole. English may be imprecise, and a paper contract could be challenged in a courtroom, but with smart contracts, there is no need for a court, since the contracts are governed by the laws of physics (the VM).
When the stakes are real and consequences real, more money and smart people will be attracted to the platform, and over time smart contracts will become more robust. Without real consequences, what is the incentive to participate if the rules can change when they don’t always go in your favor?